Why did my contacts and calendar stop syncing?

I've got a new OnePlus 2 since last month, and when I got it I set it up so that my outlook.com account would sync with Google Calendar and Contacts. Since a few days however the sync has stopped working altogether, and I've noticed that in the Gmail app I no longer have the option to toggle contact and calendar sync on and off. Can I change this back?

For the moment I'm using Outlook app which works fine, accept that the voice assistant won't allow me to put in anything in the calendar there. The contacts sync to the main contact app from there so that's fine, I just need a solution for the calendar.

I can but I want to keep one account for my contacts (outlook.com). The contact sync is actually not a big deal because the contacts app recognises the outlook app so I can import from there. It's the calendar sync that I really miss.

I can but I want to keep one account for my contacts (outlook.com). The contact sync is actually not a big deal because the contacts app recognises the outlook app so I can import from there. It's the calendar sync that I really miss.

Ok I've found the problem, it's the most recent exchange services update (see negative reviews in play store). I use Mailwise now which works for the calendar. I still have issues with contacts:

When I change the picture for my contacts (in contacts, Outlook account) it will delete this picture in the next sync. Mailwise lets me access my exchange account, but the pictures I get from there are blurry and I can't change those. Any ideas on what I can do?